A microwave energy moderating bag is disclosed and claimed in continuation-in-part application Ser. No. 837,074, now abandoned which was concurrently filed with the present application on Sept. 28, 1977, and which is hereby incorporated by reference. Such a bag comprises a foil such as aluminum foil which foil may, under some circumstances, precipitate spontaneous electrical arcing when disposed in a microwave energy field. An exemplary embodiment of such a bag is shown in FIG. 14 of the continuation-in-part application to have a longitudinally extending medial seam 60, a bottom seam 61, and a tab-type, adhesive-securable, top closure means 75. Briefly, as compared to that bag construction, the present invention is a microwave energy moderating bag comprising improved side seams, and an improved top closure which are so configured that such spontaneous electrical arcing as described above is substantially obviated.